The present invention relates generally to an information storage, and more particularly to an electronic latch unit for a disc drive. The present invention is suitable, for example, for an electromagnetic latch unit in a hard disc drive (“HDD”).
Along with the recent spread of the Internet etc., a demand for providing a less expensively HDD increases. In addition, a further miniaturization is promoted with widespread portable HDDs and the improvement of the shock resistance is necessary to stably use them in various environments.
The HDD typically includes a disc that serves as a recording medium, and a head stack assembly (“HAS”) that supports a head and moves the head to a target position on the disc. The HSA includes a carriage (also referred to as an “actuator”, an “E-block” due to its E-shaped section or “actuator (“AC”) block”) which is rotated around a shaft by the motor, a suspension attached to a support portion of the carriage (which is referred to as an “arm” hereinafter), and a magnetic head part supported on the suspension. The magnetic head part includes a fine head core (simply referred to as a “head” hereinafter) that records and reproduces a signal, and a (head) slider that supports the head and floats above the disc.
One known conventional shock resistance mechanism is a ramp loading system that retreats the slider from the disc in stopping the disc rotation, and holds the slider on a ramp. Nevertheless, the carriage at this state receiving the external impact would rotate, colliding the slider with the disc, damaging the head, and losing the disc data. Accordingly, an electromagnetic latch unit as another proposed shock resistance mechanism engages with the carriage's end opposite to the suspension while the slider is being held on the ramp (see, for example, Japanese Patent Applications, Publication Nos. 2002-190169, 2003-68038, and 2006-48768).
The conventional electromagnetic latch unit is often configured so that the latch part and an electromagnet are mounted in the internal space on the front side of the housing. The electromagnetic latch unit magnetically locks the latch part that latches the carriage end and, in rotating the disc, unlocks the latch part and moves the latch part to the unlatch position. A controller in the printed board fixed on the rear surface of the housing controls latching and unlatching. A magnet is embedded in the latch part, and held at a predetermined height from the HDD housing. The electromagnet includes a coil and a core (or yoke), and the coil is connected to the printed board via a lead wire.
However, a connection of the coil to the printed board expensively requires various steps of: (1) piercing the housing and threading the lead wire; (2) sealing the pierce to maintain the inside of the housing airtight; (3) mounting the printed board with a connector, and connecting the connector with the controller; (4) connecting the lead wire to a land of the flexible printed circuit (“FPC”) board connected with the connector; and (5) baking the housing so that the gas generated from the coil does not contaminate the inside of the housing. In addition, the disconnection of the lead wire lowers the yield, and the electromagnetic latch unit provided in the housing precludes a further miniaturization of the housing.
Japanese Patent Application, Publication No. 2002-190169, FIG. 6, provides the latch part in the housing, and arranges the electromagnet outside housing. The housing is located between the latch part and the electromagnet, possibly causing the electromagnetic efficiency to become worse than the housing at accommodates both the latch part and the electromagnet in its internal space. In addition, this prior art reference is unsuitable for the economical efficiency and the miniaturization, because this prior art reference does not provide the housing with a flat bottom surface suitable for the opposite printed board,